Modern automotive vehicle engines are generally equipped with fuel injectors for injecting fuel (e.g. gasoline or diesel fuel) into the individual cylinders of the engine. The fuel injectors are coupled to a source of high pressure fuel that is delivered to the injectors by way of a fuel delivery system. The fuel injectors typically employ a valve needle that is actuated to disengage and re-engage an associated valve seat so as to control the amount of high pressure fuel that is metered from the fuel delivery system and injected into a corresponding engine cylinder. It is known to use solenoid operated injectors in which an electrically driven solenoid is operably connected to the valve needle. Energising the solenoid causes the valve needle to disengage from its seat, thus permitting fuel delivery, and de-energising the solenoid causes the valve needle to re-engage it seat, thus preventing fuel delivery.
It is also known to use piezoelectrically operated fuel injectors that act either directly on the valve needle, or indirectly on the valve needle by way of a servo valve arrangement, to cause movement of the valve needle.
The injectors of the engine are controlled by an electrical drive arrangement. FIG. 1 shows a simplified schematic of a known drive arrangement 2 which includes an injector driver stage 4 that is supplied with power from a vehicle power supply 6, typically the vehicle battery, and provides power and control inputs to one or more fuel injectors 8 (two of which are shown in FIG. 1).
The injector driver stage 4 is a circuit arrangement that is configured to select a specific one of the injectors 8 for operation and to apply an operating voltage thereto. The functionality of the injector driver stage 4 is controlled by an Engine Control Unit 10 (ECU) of the vehicle within which it is installed.
A known problem is that such electrical drive arrangements do not operate under ideal conditions and are typically supplied with electrical power that is subject to spurious electrical oscillations, hereinafter referred to as ‘noise’. A significant proportion of power supply noise can be compensated for by the injector drive stage 4 under the control of the ECU 10 since some sources of noise are predictable. However, some sources of noise are not predictable and such noise affects detrimentally the level of control that the ECU 10 has over the operational timing of the injectors 8.